The present invention relates to a paging receiver and, more particularly, to a paging receiver having alert means implemented as a speaker or similar current driven alert means and a light emitting diode (LED).
It is a common practice with a paging receiver to alert the user thereof to a call by the sounding of a speaker and the flashing of an LED. Usually, such alert means are driven by a battery incorporated in the paging receiver and having an open circuit voltage of about 1.5 volts (hereinafter referred to as a 1 volt group battery).
The paging receiver has a receiver section for receiving and demodulating a radio frequency (RF) signal, a ROM (Read Only Memory) storing a paging number assigned to the receiver, and a decoder for comparing a paging number included in the demodulated output of the receiver section with the content of the ROM and, if the former is identical with the latter, producing a drive pattern signal which has an intermittent pattern. The paging receiver causes the speaker to sound intermittently and the LED to flash, both in the pattern of the drive pattern signal, thereby alerting the user to the reception of a call.
Since a voltage of about 1.7 volts is necessary for the LED to turn on, the output voltage of the 1 volt group battery does not suffice. For this reason, a paging receiver of the type using a 1 volt group battery has a boosting circuit for LED drive.
The currents needed to drive the speaker and LED are respectively about 60 milliamperes and about 10 milliamperes although they slightly change due to the drop of the battery voltage. These drive currents assume a considerable proportion of the entire current necessary for the various components of the paging receiver to be driven. Therefore, the voltage of the battery noticeably drops while the speaker sounds and the LED flashes.
The battery for powering a paging receiver is generally implemented by a coin type battery such as a nickel-cadmium battery or an air-zinc battery since this type of battery is small size. The current capacity of such a battery is so small that the above-mentioned voltage drop is considerable, especially when ambient temperature is low.
On the other hand, a conventional paging receiver drives the speaker and LED by drive currents having an identical signal pattern, i.e., drives them at the same time. This aggravates the voltage drop of the battery since the speaker and LED each needs a great drive current, as stated earlier. As a result, at the final stage of the life of the battery or in a low temperature condition, a drive current great enough to insure the luminance of the LED is not achievable.